An engine may be started by injecting fuel more than once during a cycle of a cylinder. One method that controls injection in this way is presented in U.S. Pat. No. 6,578,551. This method provides two fuel injection events during the first combustion cycle of the respective cylinders and then transitions to a single injection event per cylinder as the engine is started. Initially, fuel is injected simultaneously to all cylinders and then fuel is simultaneously injected to cylinders one and three before a first combustion event in the respective cylinders. The second injection to cylinder one occurs during the intake stroke of cylinder one while the second injection to cylinder three occurs during the exhaust stroke of cylinder three. The fuel injections are delivered to the intake ports and are inducted into the cylinders during the respective intake strokes. According to the above-mentioned specification, this strategy can reduce starting time and may reduce HC emissions.
The above-mentioned method can also have several disadvantages. For example, the method appears to rely on engine position information from two position sensors (one that provides angle information and one that provides phase information) to start the engine and does not appear to provide a starting procedure if the phase sensor information is not available. In other words, if the engine phase signal is degraded then it is not apparent that the respective strokes of the cylinders can be determined. Therefore, fuel injection as is described during the initial intake stroke of cylinder one and the exhaust stroke of cylinder three may not be assured. As a result, the engine may not start or it may be possible to start the engine, but the starting time may be increased by as much as two engine revolutions. Further, the fueling for each of the engine cylinders may be out of phase with respect to the desired cylinder fuel timing as the engine operates. Consequently, it may be possible to inject fuel during an open intake valve interval when intending to inject during a closed valve interval, for example.
The inventor herein has recognized the above-mentioned disadvantages and has developed a method to control engine valves during stopping and starting that offers substantial improvements.